Jakarta ee 如何在Vaadin中获取CDIView中的UI实例？

我有MyUI课程

@Theme("mytheme")
@CDIUI("")
public class MyUI extends UI {

@Inject
LoginView loginView;

@Override
protected void init(VaadinRequest vaadinRequest) {
    setContent(loginView);
}

...

我有一个用

@PostConstruct

@UIScoped
@CDIView(LoginView.VIEWNAME)
public class LoginView extends VerticalLayout implements CustomView {

    @PostConstruct
    public void initView() {

        //initializations elements 
        Component loginForm = buildLoginForm();
        addComponent(loginForm);
        setComponentAlignment(loginForm, Alignment.MIDDLE_CENTER);

        Notification notification = new Notification("Demo");
        notification.setDescription("<span>DEMO</span>");
        notification.setHtmlContentAllowed(true);
        notification.setStyleName("tray dark small closable login-help");
        notification.setPosition(Position.BOTTOM_CENTER);
        notification.setDelayMsec(20000);
        notification.show(Page.getCurrent()); // NullPointerException

    }
}

我的问题是如何在呈现视图元素的过程中使用UI实例

我发现了一个部分解决方案，它将所有元素的定义放入一个configure方法中，方法如下：

public void configure() {
    //initializations elements
    Component loginForm = buildLoginForm();
    addComponent(loginForm);
    setComponentAlignment(loginForm, Alignment.MIDDLE_CENTER);

    Notification notification = new Notification("Demo");
    notification.setDescription("<span>DEMO</span>");
    notification.setHtmlContentAllowed(true);
    notification.setStyleName("tray dark small closable login-help");
    notification.setPosition(Position.BOTTOM_CENTER);
    notification.setDelayMsec(20000);
    notification.show(Page.getCurrent());
}

---

最后，在同事的帮助下，我找到了一个解决方案：

有必要以这种方式使用CDIViewProvider

@Theme("mytheme")
@CDIUI("")
public class MyUI extends UI {

@Inject
LoginView loginView;

@Inject
private CDIViewProvider viewProvider;

@Override
protected void init(VaadinRequest vaadinRequest) {
    Navigator navigator = new Navigator(this, this);
    navigator.addProvider(viewProvider);
    navigator.navigateTo("login");
}

在类中，定义视图的名称，并将视图元素的所有定义放入entering方法中

@UIScoped
@CDIView(LoginView.VIEWNAME)
public class LoginView extends VerticalLayout implements CustomView {

    public static final String VIEWNAME = "login";

   //...
   //other methods
   //... 

   @Override
   public void enter(ViewChangeListener.ViewChangeEvent event) {
      //initializations elements
      Component loginForm = buildLoginForm();
      addComponent(loginForm);
      setComponentAlignment(loginForm, Alignment.MIDDLE_CENTER);

      Notification notification = new Notification("Demo");
      notification.setDescription("<span>DEMO</span>");
      notification.setHtmlContentAllowed(true);
      notification.setStyleName("tray dark small closable login-help");
      notification.setPosition(Position.BOTTOM_CENTER);
      notification.setDelayMsec(20000);
      notification.show(Page.getCurrent());
    }
}

@UIScoped
@CDIView（LoginView.VIEWNAME）
公共类LoginView扩展了VerticalLayout，实现了CustomView{
公共静态最终字符串VIEWNAME=“login”；
//...
//其他方法
//... 
@凌驾
公共无效输入（ViewChangeListener.ViewChangeEvent事件）{
//初始化元素
组件loginForm=buildLoginForm（）；
addComponent（loginForm）；
setComponentAlignment（loginForm，Alignment.MIDDLE_CENTER）；
通知通知=新通知（“演示”）；
通知。设置说明（“演示”）；
通知。setHtmlContentAllowed（true）；
notification.setStyleName（“托盘黑色小可关闭登录帮助”）；
通知。设置位置（位置。底部_中心）；
通知。setDelayMsec（20000）；
notification.show（Page.getCurrent（））；
}
}

@Theme("mytheme")
@CDIUI("")
public class MyUI extends UI {

@Inject
LoginView loginView;

@Inject
private CDIViewProvider viewProvider;

@Override
protected void init(VaadinRequest vaadinRequest) {
    Navigator navigator = new Navigator(this, this);
    navigator.addProvider(viewProvider);
    navigator.navigateTo("login");
}

@UIScoped
@CDIView(LoginView.VIEWNAME)
public class LoginView extends VerticalLayout implements CustomView {

    public static final String VIEWNAME = "login";

   //...
   //other methods
   //... 

   @Override
   public void enter(ViewChangeListener.ViewChangeEvent event) {
      //initializations elements
      Component loginForm = buildLoginForm();
      addComponent(loginForm);
      setComponentAlignment(loginForm, Alignment.MIDDLE_CENTER);

      Notification notification = new Notification("Demo");
      notification.setDescription("<span>DEMO</span>");
      notification.setHtmlContentAllowed(true);
      notification.setStyleName("tray dark small closable login-help");
      notification.setPosition(Position.BOTTOM_CENTER);
      notification.setDelayMsec(20000);
      notification.show(Page.getCurrent());
    }
}